1. Field of the Invention
This invention relates to electromagnetic antenna construction and the process for fabricating the same. More particularly the invention relates to whip antenna construction with a protective coating for use with two-way portable communication equipment.
2. Prior Art
In certain types of whip antennas the conducting antenna wire is carried on a highly flexible core usually in spiral conformations. In order to give the antenna a reasonable useable life it is desirable that the core and the wire be covered to protect the assembly from the effects of weather, abrasion, and physical blows to which a whip antenna is subjected during normal use. A protective antenna cover prevents alteration in the electrical characteristics of the antenna which might result in degraded antenna performance. It is of course necessary that the covering provided be flexible so as to not impair the flexibility of the antenna.
In the prior art an antenna cable is normally constructed by spiraling conductive wire along the core length of a flexible core. A base section for the antenna is machined from stainless steel or brass. One end of the antenna cable is then press fitted into a bore at one end of the stainless steel base section. At an opposite end of the base section threads are provided so that the antenna may be mounted to the radio housing. The machined stainless steel base section conducts the RF signal between the antenna cable and the radio receiver. The antenna wire wound about its flexible core and press fitted into the base section is dipped into a vat of liquid plastic and then removed to cure. The resulting coat of plastic serves as a protective cover for the whip antenna. This protective cover protects the antenna cable and base section and yet will flex so that the flexibility of the antenna cable is not impaired.
A soft plastic cap piece is glued over the free end of the plastic coated antenna in order to provide protection to the user against the otherwise blunt end of the antenna cable. The cap piece also protects the antenna cable end from the abuses of its normal environment. Often, in the process of daily use, the cap piece will loosen and fall off the antenna cable end. If this happens the antenna cable end is left exposed to the weather and physical effects of its normal use which results in degradation of the antennas electrical performance.
When in use often the radio is carried in a belt holster around the user's waist. If the portable radio has rechargeable batteries it is most likely recharged in a device which cradles the radio housing. In both of these holding arrangements users have found it convenient to remove the two-way radio from its holder by improperly using the antenna as a handle. The protective cover construction of the prior art does not provide sufficient protection for the antenna when it is subjected to this type of use. From such use, the antenna cap piece may be forced off and the plastic coating is subject to sliding along the antenna length exposing the base portion of the antenna to the environment. Moreover without an antenna cap piece the exposed antenna cable end could cause physical harm to the user since the portable radio is held close to the face during normal operation. Such disintegration of the antennas protective coating usually results in degradation or grounding of the antenna through corrosion, collection of dirt and other deterioration resulting from exposure to the environment.
Since the antenna comprises the simplest technical construction in a two-way radio, the fact that it is subject to heavy physical abuse by the user has in the past been a problem not sufficiently appreciated. In many applications this has resulted in an antenna life span of only a few months.
It is therefore an object of this invention to provide a simple, yet rugged, whip antenna construction which protects and improves antenna electrical performance.
It is a further object of the present invention to provide a simple and inexpensive to manufacture whip antenna which is of a rugged construction which can simultaneously withstand the abuse of being misused as a handle.